Predictors of moderate-severe functional limitation after primary Total Knee Arthroplasty (TKA): 4701 TKAs at 2-years and 2935 TKAs at 5-years.

OBJECTIVE

Investigate whether body mass index (BMI), comorbidity, gender and age predict patient-reported functional limitation 2- and 5-years after primary Total Knee Arthroplasty (TKA).

METHODS

Overall moderate-severe activity limitation was defined as > or = 2 activities (walking, stairs, rising from chair) with moderate-severe limitation. Complete dependence on walking aids or inability to walk was assessed (reference, no dependence). Multivariable logistic regression models were adjusted additionally for income, diagnosis, distance from medical center, American Society of Anesthesiologists (ASA) score and implant type.

RESULTS

Overall moderate-severe activity limitation was reported by 20.7% at 2-years and 27.1% at 5-years. Significantly predictors of overall moderate-severe activity limitation 2-years post-TKA (odds (95% confidence interval)) were: BMI 30-34.9, 1.5 (1.0, 2.0), 35-39.9, 1.8 (1.3, 2.7) and > or = 40, 3.0 (2.0, 4.5) vs BMI < or = 25; higher Deyo-Charlson index, 1.7 (1.4, 2.2) per 5-point increase; female gender, 2.0 (1.7, 2.5); age 71-80, 2.1 (1.5, 2.8) and age > 80, 4.1 (2.7, 6.1) vs age < or = 60. At 5-years post-TKA, significant predictors of overall moderate-severe activity limitation were: BMI 35-39.9, 2.1 (1.4, 3.3) and > or = 40, 3.9 (2.3, 6.5); higher Deyo-Charlson index, 1.4 (1.0, 1.8); female gender, 2.2 (1.7, 2.7); age 71-80, 2.4 (1.7, 3.5) and age > 80, 4.7 (2.8, 7.9). Complete dependence on walking aids was significantly higher at 2- and 5-years, respectively, in patients with: higher comorbidity, 2.3 (1.5, 3.3) and 2.1 (1.4, 3.2); female gender 2.4 (1.5, 3.9) and 1.7 (1.1, 2.6); age 71-80, 1.4 (0.8, 2.6) and 1.5 (0.8, 2.8); and age > 80, 3.2 (1.6, 6.7) and 5.1 (2.3, 11.0).

CONCLUSIONS

Modifiable (BMI, comorbidity) and non-modifiable predictors (age, gender) increased the risk of functional limitation and walking-aid dependence after primary TKA. Interventions targeting comorbidity and BMI pre-operatively may positively impact function post-TKA.